libavdevice/dv1394.h

00001 /*00002 * DV input/output over IEEE 1394 on OHCI chips00003 * Copyright (C)2001 Daniel Maas <dmaas@dcine.com>00004 * receive, proc_fs by Dan Dennedy <dan@dennedy.org>00005 *00006 * based on:00007 * video1394.h - driver for OHCI 1394 boards00008 * Copyright (C)1999,2000 Sebastien Rougeaux <sebastien.rougeaux@anu.edu.au>00009 * Peter Schlaile <udbz@rz.uni-karlsruhe.de>00010 *00011 * This file is part of FFmpeg.00012 *00013 * FFmpeg is free software; you can redistribute it and/or00014 * modify it under the terms of the GNU Lesser General Public00015 * License as published by the Free Software Foundation; either00016 * version 2.1 of the License, or (at your option) any later version.00017 *00018 * FFmpeg is distributed in the hope that it will be useful,00019 * but WITHOUT ANY WARRANTY; without even the implied warranty of00020 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU00021 * Lesser General Public License for more details.00022 *00023 * You should have received a copy of the GNU Lesser General Public00024 * License along with FFmpeg; if not, write to the Free Software00025 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA00026 */00027
00028 #ifndef AVDEVICE_DV1394_H00029 #define AVDEVICE_DV1394_H00030 00031#define DV1394_DEFAULT_CHANNEL 6300032#define DV1394_DEFAULT_CARD 000033#define DV1394_RING_FRAMES 2000034 00035#define DV1394_WIDTH 72000036#define DV1394_NTSC_HEIGHT 48000037#define DV1394_PAL_HEIGHT 57600038 00039 /* This is the public user-space interface. Try not to break it. */00040
00041#define DV1394_API_VERSION 0x2001112700042 00043 /* ********************00044 ** **00045 ** DV1394 API **00046 ** **00047 ********************00048 00049 There are two methods of operating the DV1394 DV output device.00050 00051 1)00052 00053 The simplest is an interface based on write(): simply write00054 full DV frames of data to the device, and they will be transmitted00055 as quickly as possible. The FD may be set for non-blocking I/O,00056 in which case you can use select() or poll() to wait for output00057 buffer space.00058 00059 To set the DV output parameters (e.g. whether you want NTSC or PAL00060 video), use the DV1394_INIT ioctl, passing in the parameters you00061 want in a struct dv1394_init.00062 00063 Example 1:00064 To play a raw .DV file: cat foo.DV > /dev/dv139400065 (cat will use write() internally)00066 00067 Example 2:00068 static struct dv1394_init init = {00069 0x63, (broadcast channel)00070 4, (four-frame ringbuffer)00071 DV1394_NTSC, (send NTSC video)00072 0, 0 (default empty packet rate)00073 }00074 00075 ioctl(fd, DV1394_INIT, &init);00076 00077 while(1) {00078 read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE );00079 write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE );00080 }00081 00082 2)00083 00084 For more control over buffering, and to avoid unnecessary copies00085 of the DV data, you can use the more sophisticated the mmap() interface.00086 First, call the DV1394_INIT ioctl to specify your parameters,00087 including the number of frames in the ringbuffer. Then, calling mmap()00088 on the dv1394 device will give you direct access to the ringbuffer00089 from which the DV card reads your frame data.00090 00091 The ringbuffer is simply one large, contiguous region of memory00092 containing two or more frames of packed DV data. Each frame of DV data00093 is 120000 bytes (NTSC) or 144000 bytes (PAL).00094 00095 Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES00096 ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl00097 or select()/poll() to wait until the frames are transmitted. Next, you'll00098 need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer00099 frames are clear (ready to be filled with new DV data). Finally, use00100 DV1394_SUBMIT_FRAMES again to send the new data to the DV output.00101 00102 00103 Example: here is what a four-frame ringbuffer might look like00104 during DV transmission:00105 00106 00107 frame 0 frame 1 frame 2 frame 300108 00109 *--------------------------------------*00110 | CLEAR | DV data | DV data | CLEAR |00111 *--------------------------------------*00112 <ACTIVE>00113 00114 transmission goes in this direction --->>>00115 00116 00117 The DV hardware is currently transmitting the data in frame 1.00118 Once frame 1 is finished, it will automatically transmit frame 2.00119 (if frame 2 finishes before frame 3 is submitted, the device00120 will continue to transmit frame 2, and will increase the dropped_frames00121 counter each time it repeats the transmission).00122 00123 00124 If you called DV1394_GET_STATUS at this instant, you would00125 receive the following values:00126 00127 n_frames = 400128 active_frame = 100129 first_clear_frame = 300130 n_clear_frames = 200131 00132 At this point, you should write new DV data into frame 3 and optionally00133 frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that00134 it may transmit the new frames.00135 00136 ERROR HANDLING00137 00138 An error (buffer underflow/overflow or a break in the DV stream due00139 to a 1394 bus reset) can be detected by checking the dropped_frames00140 field of struct dv1394_status (obtained through the00141 DV1394_GET_STATUS ioctl).00142 00143 The best way to recover from such an error is to re-initialize00144 dv1394, either by using the DV1394_INIT ioctl call, or closing the00145 file descriptor and opening it again. (note that you must unmap all00146 ringbuffer mappings when closing the file descriptor, or else00147 dv1394 will still be considered 'in use').00148 00149 MAIN LOOP00150 00151 For maximum efficiency and robustness against bus errors, you are00152 advised to model the main loop of your application after the00153 following pseudo-code example:00154 00155 (checks of system call return values omitted for brevity; always00156 check return values in your code!)00157 00158 while( frames left ) {00159 00160 struct pollfd *pfd = ...;00161 00162 pfd->fd = dv1394_fd;00163 pfd->revents = 0;00164 pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive)00165 00166 (add other sources of I/O here)00167 00168 poll(pfd, 1, -1); (or select(); add a timeout if you want)00169 00170 if(pfd->revents) {00171 struct dv1394_status status;00172 00173 ioctl(dv1394_fd, DV1394_GET_STATUS, &status);00174 00175 if(status.dropped_frames > 0) {00176 reset_dv1394();00177 } else {00178 for(int i = 0; i < status.n_clear_frames; i++) {00179 copy_DV_frame();00180 }00181 }00182 }00183 }00184 00185 where copy_DV_frame() reads or writes on the dv1394 file descriptor00186 (read/write mode) or copies data to/from the mmap ringbuffer and00187 then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new00188 frames are availble (mmap mode).00189 00190 reset_dv1394() is called in the event of a buffer00191 underflow/overflow or a halt in the DV stream (e.g. due to a 139400192 bus reset). To guarantee recovery from the error, this function00193 should close the dv1394 file descriptor (and munmap() all00194 ringbuffer mappings, if you are using them), then re-open the00195 dv1394 device (and re-map the ringbuffer).00196 00197 */00198
00199
00200 /* maximum number of frames in the ringbuffer */00201#define DV1394_MAX_FRAMES 3200202 00203 /* number of *full* isochronous packets per DV frame */00204#define DV1394_NTSC_PACKETS_PER_FRAME 25000205#define DV1394_PAL_PACKETS_PER_FRAME 30000206 00207 /* size of one frame's worth of DV data, in bytes */00208#define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)00209#define DV1394_PAL_FRAME_SIZE (480 * DV1394_PAL_PACKETS_PER_FRAME)00210 00211
00212 /* ioctl() commands */00213
00214 enum {
00215 /* I don't like using 0 as a valid ioctl() */00216DV1394_INVALID = 0,
00217
00218
00219 /* get the driver ready to transmit video.00220 pass a struct dv1394_init* as the parameter (see below),00221 or NULL to get default parameters */00222DV1394_INIT,
00223
00224
00225 /* stop transmitting video and free the ringbuffer */00226DV1394_SHUTDOWN,
00227
00228
00229 /* submit N new frames to be transmitted, where00230 the index of the first new frame is first_clear_buffer,00231 and the index of the last new frame is00232 (first_clear_buffer + N) % n_frames */00233DV1394_SUBMIT_FRAMES,
00234
00235
00236 /* block until N buffers are clear (pass N as the parameter)00237 Because we re-transmit the last frame on underrun, there00238 will at most be n_frames - 1 clear frames at any time */00239DV1394_WAIT_FRAMES,
00240
00241 /* capture new frames that have been received, where00242 the index of the first new frame is first_clear_buffer,00243 and the index of the last new frame is00244 (first_clear_buffer + N) % n_frames */00245DV1394_RECEIVE_FRAMES,
00246
00247
00248DV1394_START_RECEIVE,
00249
00250
00251 /* pass a struct dv1394_status* as the parameter (see below) */00252DV1394_GET_STATUS,
00253 };
00254
00255
00256
00257enumpal_or_ntsc {
00258DV1394_NTSC = 0,
00259DV1394_PAL00260 };
00261
00262
00263
00264
00265 /* this is the argument to DV1394_INIT */00266struct dv1394_init {
00267 /* DV1394_API_VERSION */00268unsignedintapi_version;
00269
00270 /* isochronous transmission channel to use */00271unsignedintchannel;
00272
00273 /* number of frames in the ringbuffer. Must be at least 200274 and at most DV1394_MAX_FRAMES. */00275unsignedintn_frames;
00276
00277 /* send/receive PAL or NTSC video format */00278enumpal_or_ntscformat;
00279
00280 /* the following are used only for transmission */00281
00282 /* set these to zero unless you want a00283 non-default empty packet rate (see below) */00284unsignedlongcip_n;
00285unsignedlongcip_d;
00286
00287 /* set this to zero unless you want a00288 non-default SYT cycle offset (default = 3 cycles) */00289unsignedintsyt_offset;
00290 };
00291
00292 /* NOTE: you may only allocate the DV frame ringbuffer once each time00293 you open the dv1394 device. DV1394_INIT will fail if you call it a00294 second time with different 'n_frames' or 'format' arguments (which00295 would imply a different size for the ringbuffer). If you need a00296 different buffer size, simply close and re-open the device, then00297 initialize it with your new settings. */00298
00299 /* Q: What are cip_n and cip_d? */00300
00301 /*00302 A: DV video streams do not utilize 100% of the potential bandwidth offered00303 by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,00304 DV devices must periodically insert empty packets into the 1394 data stream.00305 Typically there is one empty packet per 14-16 data-carrying packets.00306 00307 Some DV devices will accept a wide range of empty packet rates, while others00308 require a precise rate. If the dv1394 driver produces empty packets at00309 a rate that your device does not accept, you may see ugly patterns on the00310 DV output, or even no output at all.00311 00312 The default empty packet insertion rate seems to work for many people; if00313 your DV output is stable, you can simply ignore this discussion. However,00314 we have exposed the empty packet rate as a parameter to support devices that00315 do not work with the default rate.00316 00317 The decision to insert an empty packet is made with a numerator/denominator00318 algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.00319 You can alter the empty packet rate by passing non-zero values for cip_n00320 and cip_d to the INIT ioctl.00321 00322 */00323
00324
00325
00326struct dv1394_status {
00327 /* this embedded init struct returns the current dv139400328 parameters in use */00329struct dv1394_initinit;
00330
00331 /* the ringbuffer frame that is currently being00332 displayed. (-1 if the device is not transmitting anything) */00333intactive_frame;
00334
00335 /* index of the first buffer (ahead of active_frame) that00336 is ready to be filled with data */00337unsignedintfirst_clear_frame;
00338
00339 /* how many buffers, including first_clear_buffer, are00340 ready to be filled with data */00341unsignedintn_clear_frames;
00342
00343 /* how many times the DV stream has underflowed, overflowed,00344 or otherwise encountered an error, since the previous call00345 to DV1394_GET_STATUS */00346unsignedintdropped_frames;
00347
00348 /* N.B. The dropped_frames counter is only a lower bound on the actual00349 number of dropped frames, with the special case that if dropped_frames00350 is zero, then it is guaranteed that NO frames have been dropped00351 since the last call to DV1394_GET_STATUS.00352 */00353 };
00354
00355
00356 #endif /* AVDEVICE_DV1394_H */